1. Field of the Invention
This invention relates to the production of grain flour, primarily wheat flour, and more particularly to an apparatus for the dehusking of such grain preparatory to the grinding thereof to produce the flour.
2. Description of the Prior Art
After removal of the grain from the heads of the stalks of cereal plants, it is usual, at least in modern western technology, to mill it by passing a stream of it successively through a "train" of paired rollers. These rollers, when at the upstream end of a flour mill, have figured or otherwise roughened surfaces and are journalled so as to provide a nip therebetween commensurate with grain size whereas, at the downstream end of such a mill, the rollers are journalled so as to have a much narrower nip and are provided with substantially smooth surfaces.
During its passage through such a train of pairs of prior known rollers, the grain is only partially dehusked and also, inevitably, partially crushed and/or ground at each stage. Between the stages and especially in the region of the upstream stages the grain is winnowed, or subjected to a shaking process which may be accompanied by a fanning or blowing step, either of which steps is intended to blow the bran, that is to say, comminuted grain husk, free from the heavier material which is composed partly of grain kernel and partly of those parts of the husk and other unwanted material not yet removed.
It is a disadvantage of the above-described process--which is known as the "break system" that a considerable number of rollers (usually between eight and thirty-six, but often more than thirty-two) must be employed to produce flour. However, even the use of perhaps thirty-two rollers does not give a very high grade of flour because it is not practicable to remove all the bran from the kernels.
This bran has little or no dietary value as it is too finely comminuted to be readily hydrated in the gut, and so contributes virtually nothing to the desirable fibre component of a diet. More seriously the remaining detritus in the flour will include not only the powdered husk but also unspecified dirt and tiny particles of insects such as curculionidea or weevils.
Attempts have been made to improve the quality of milled flour by increasing the effectiveness of the winnowing step between the rolling stages of the "break system" of milling, but this has proved to be disastrously uneconomic because a high proportion of the flour itself is also lost. This overall contretemps has produced a situation in which the chefs of many high quality restaurants insist on hand-ground flour, needless to say at high cost.